[abstract] DIVER THERMAL STATUS AS A RISK FACTOR FOR DECOMPRESSION SICKNESS (DCS).

Abstract

INTRODUCTION: Cold working divers are widely presumed to be at increased risk for DCS, but there is little unequivocal support for this presumption. This study was conducted to test whether diver thermal status is a risk factor for DCS. METHODS: US Navy divers completed 357 water-immersed, working air decompression dives to 120 fsw in the NEDU Ocean Simulation Facility. All dives were identical except for bottom time (BT) and diver thermal status during certain phases of the dives. Divers completed either the compression and working bottom phase, or the resting decompression, semi-nude in water that was either "warm" (W) at 97 F or "cold" (C) at 80 F. (CW represents cold compression and time at bottom followed by warm decompression.) All decompressions were 120 fsw/70 min US Navy Standard Air (91 min decompression), and were followed by a 4-hr resting observation period at 78 F. RESULTS: Eleven DCS cases occurred in 112 WC dives: 7 in 32 dives with 30-min BT, and 4 in 80 dives with 25-min BT. Two DCS cases occurred in 245 CW dives: 0 in 80 dives with 30-min BT, 0 in 8 dives with 50-min BT, and 2 in 157 dives with 70-min BT. Eight DCS cases involved "hand" symptoms (4 Type I, 2 Type II and 2 cutis marmorata). The remaining 5 cases were "classic" joint pain, with and without paraesthesia. At the extremes of thermal status and BT examined, DCS incidence (+/-95percent confidence limits) was 1.3percent (0.15 - 4.5) for 120 fsw/70 min CW dives compared with 21.9percent (9.3 - 40.0) for 120 fsw/30 min WC dives. CONCLUSION: Diver thermal status has a large effect on DCS risk under the conditions tested, with warm decompression favoring lower DCS risk. Appropriate manipulation of diver thermal status during different phases of a dive might afford operationally significant decreases in diver DCS susceptibility.